This study was designed to evaluate effects of varying type of forage and feeding times of rumen degradable nitrogen sources on milk production, digestibility, feeding behavior and rumen metabolites of lactating dairy cows. Twelve multiparous (100 ± 10 d in milk) Holstein dairy cows were used in incomplete Latin square design (five 21-d periods) with a 2 × 3 factorial arrangement of treatments. All diets had a 50:50 forage-to-concentrate ratio, contained 16% CP, and were formulated to be equal in rumen-degradable protein. Treatments include different alfalfa hay-to-corn-silage ratios (35:15 and 15:35) and different feeding times of the rumen degradable nitrogen sources: 1- total mixed ration (TMR) was offered once daily in the morning (0900); 2- part of soybean meal was offered at 2100; 3- part of urea was offered at 2100. Data were analyzed using the mixed procedures of SAS. Diets based on corn silage and feeding soybean meal at night increased milk and ECM yield (P < 0.05) (ALFA1 = 32.06, ALFA2 = 33.95, ALFA3 = 32.25, CORN1 = 32.69, CORN2 = 34.17, CORN3 = 33.91; SEM = 0.55). Dry matter, organic matter and neutral detergent fiber digestibility numerically increased in cows feed corn silage diets (P < 0.09) and not affected by feeding times of rumen degradable nitrogen sources (P < 0.25). Feeding urea at night increased ruminating and chewing time (min/d and min/kg of NDF intake) in alfalfa hay based diets (P < 0.05), but not in corn silage based diets. Standing ruminating (min/d) was higher for alfalfa hay fed cows (P < 0.01) and resting ruminating (min/d) was higher for corn silage fed cows (P < 0.01). Total volatile fatty acids and molar proportions not affected by treatments (P > 0.15). Corn silage based diets improved milk production and digestibility.